Graduate Thesis Or Dissertation

 

Structure and stratigraphy of the Jefferson Mountain Area Centennial Range, Idaho-Montana Public Deposited

https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/k643b458s

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  • The Jefferson Mountain area, located at the eastern end of the Centennial Mountains in Fremont County, Idaho and Beaverhead County, Montana, is approximately 42 square miles in size. The area contains exposed metamorphic, sedimentary, and volcanic rocks ranging in age from Precambrian to Tertiary. Approximately 2,500 feet of Paleozoic and Mesozoic sedimentary rocks lie between a basal complex of Precambrian metamorphic rocks and overlying Tertiary volcanics and Quaternary alluvium. The Precambrian rocks in the area are regionally metamorphosed sedimentary rocks of the Cherry Creek Group that include hornblende schists, granite gneisses, quartzites, and dolomites. Eleven Paleozoic formations occur in the area, representing all of the Paleozoic periods except Ordovician and Silurian. The dominant rock types representing the Paleozoic are dolomites and limestones, but sandstone and shales make up a significant part of the section. The Triassic Dinwoody Formation, a silty dolomite, is the only representative of Mesozoic deposition in the thesis area. The volcanics in the area are part of the late Tertiary Yellowstone Tuff and Snake River volcanics of eastern Idaho and northwestern Wyoming. Pliocene and Early Pleistocene downwarping of the Snake River Plain resulted in block-faulting along its northeastern margin, forming the Centennial Range, a large south-tilting cuesta. The sedimentary rocks were deposited by a series of transgressions and regressions of marine water during the evolution of the Cordilleran Geosyncline. The sedimentary rocks represent the shelf facies along the eastern margin of the miogeosyncline. Oil and gas possibilities in the area are negligible. Structural and stratigraphic relationships do not indicate any type of control for the entrapment of petroleum. The economic potentiality for phosphate mining in the area is low because of the thinness of the phosphate-bearing member of the Phosphoria Formation.
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  • File scanned at 300 ppi (Monochrome, 24-bit Color) using Capture Perfect 3.0.82 on a Canon DR-9080C in PDF format. CVista PdfCompressor 4.0 was used for pdf compression and textual OCR. Plate: Master map file scanned at 600 dpi, 24-bit color on a Paradigm ImagePRO GxT 42 HD (OEM version of ColortracSmartLF Bx 42). Image manipulated by SmartLF1.3.05.
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